Charge density effect of micelles on liquid-liquid phase separation

Liquid-liquid phase separation (LLPS) is central to the organization of biological and synthetic soft matter systems, yet how electrostatic interactions control condensation remains incompletely understood. Using coarse-grained molecular dynamics (MD) simulations, we investigate LLPS in charged micelle-polymer mixtures, focusing on how micelle charge affects phase behavior. We adopt a mapping from zeta potential (ζ) to the reduced Yukawa charge (q*), calibrated to experiments within a model oligomer-micelle mixture patterned on peptide amphiphile assemblies in the presence of dasiglucagon (DG). After identifying q_DG ≈ -6e as the effective DG charge required for LLPS, systematic variation of the micellar charge reveals a finite charge window bounded by lower and upper critical charges: increasing charge initially enhances micelle-polymer attraction and densifies the liquid complex, but at high charge, growing micelle-micelle repulsion destabilizes the dense phase. The predicted window overlaps the experimentally measured ζ values, and the ζ of glucose-associated PA-PBA lies within the island-like pocket, underscoring the dual regulatory role of electrostatics.